Whoever, being an officer or employee of the United States or of any department or agency thereof, embezzles or wrongfully converts to his own use the money or property of another which comes into his possession or under his control in the execution of such office or employment, or under color or claim of authority as such officer or employee, shall be fined under this title or not more than the value of the money and property thus embezzled or converted, whichever is greater, or imprisoned not more than ten years, or both; but if the sum embezzled is $1,000 or less, he shall be fined under this title or imprisoned not more than one year, or both.